Field of the Invention
This invention relates to a paper folding knife device of belt drive unit type for a paper folder.
In the prior art paper folding knife device for a paper folder, the adjustment of the vertical knife position requires not only adjustment of the knife shaft but also adjustment of the vertical position of the entire device body.
Therefore, a drive motor unit which is directly coupled to a head gear is simultaneously vertically moved, and it is impossible to arrange the device body and drive unit such that they are comparatively stationary. For this reason, the prior art paper folder cannt be constructed as an integral unit.
Further, in the prior art paper folding knife device a drive unit to which a motor drive unit is directly coupled, is coupled via a head gear to a shaft, on which a transmission clutch and a brake mechanism for controlling the operation of the transmission crank mechanism is provided to permit a paper folding operation with a vertical crank motion of a paper folding knife. The crank motion of the knife is brought about with the movement of the transmission clutch brake mechanism and drive motor unit directly coupled to the head gear. In the crank motion, the upward motion of the knife shaft is caused with a heavy upward load supplied through the clutch gear, while the downward motion of the knife shaft is a high speed motion in the form of a free fall due to the weight of the knife shaft and without any load. The load on the shaft of the crank mechanism varies with the vertical motion of the knife shaft. Also, when the free fall speed of the downward motion surpasses the crank speed in the downward stroke of the crank from the top dead center to the bottom dead center, a reverse load is produced, with which the drive side is driven from the driven or load side, so that backlash results. This means that there occur impact variations due to tapping of gears, resulting in gear tapping noise for every crank motion cycle. In addition, the gears wear significantly to produce very adverse effects on the motor, clutch, etc. Further, at the time of the crank coupling the load has to be increased in a short period of time. Therefore, a very high surface pressure is applied to the gears. Further, the aforementioned tapping noise and wear of the gears are extremely pronounced as the frequency of installation and removal of the clutch gear is increased with increase of the speed of paper folding operation by the crank mechanism. In this case, damage to the motor, clutch, etc. is readily liable.
Further, the prior art paper folding knife device for a paper folder is considerably large in size and requires a large installation space in addition to the fact that its anti-noise property and life are interior.
To alleviate the above drawbacks it has been contemplated to adopt a variable speed motor to cope with the load variations noted above. In this case, however, the gear mechanism is complicated, and the cost of the motor is high. Further, the mechanism as a whole is large in size, leading to a large size paper folder. From the above ground, the variable speed motor is inadequate and has not yet been employed in practice.